The present disclosure relates to a signal processing device, a signal processing method, and a computer program.
A method of digitizing audio signals for recording, reproduction, and transmission is implemented in a recording/reproducing apparatus for a tape-shaped recording medium, including an optical disc, such as a compact disc (CD), or a digital audio tape (DAT), or in digital broadcasting, such as satellite broadcasting. In such a digital audio transmission apparatus, the format has conventionally been set for the sampling frequency of 48 kHz, 44.1 kHz, or the like and the number of quantization bits of 16 bits, 24 bits, or the like for digitization.
As a method of digitizing audio signals, a method termed ΣΔ (ΣΔ) modulation has been proposed (see Yoshio Yamazaki, “AD/DA converter and Digital Filter”, Journal of Japan Society of Acoustics, Vol. 46, No. 3 (1990), pp. 251-257. In addition, a digital signal processing device which performs fade processing while switching between a delayed ΣΔ modulated signal in which a ΣΔ modulated signal is delayed and a ΣΔ re-modulated signal obtained by subjecting an input signal to the ΣΔ modulation again has been proposed (for example, JP 3318823B). The signal processing device described in JP 3318823B is configured so that a pattern detector is provided for reducing noises generated in the fade processing as much as possible and when the pattern detector detects coincidence between the delayed ΣΔ modulated signal and the ΣΔ re-modulated signal over a plurality of samples, a changeover switch switches the output state of both the signals, and then performs fade processing capable of suppressing the generation of noises.